(I'm basically just posting the obvious.)

You can purchase Jesper Kyd's music on Amazon MP3 and (some) iTunes. Check out his website to see - http://www.jesperkyd.com/

(It doesn't seem obvious on his site but you can buy some soundtracks through Amazon MP3 rather than physical CD - for example, Hitman: Contracts)

Or you can listen to many, perhaps /all/, full soundtracks on YouTube; it's just a matter of searching.

Holy cow, I had no idea the soundtrack CDs are out of print! Good thing I bought these many, many years ago. I don't own many game soundtracks on CD, only the Hitman series and Quest for Glory V, but those are so unbelievably good!